1. Field of the Invention
The present invention relates to a non-return valve for a fuel tank, which is provided on a downstream end of a fuel filling pipe of a fuel tank of an automobile or the like.
2. Description of the Related Art
As shown in FIG. 1, a variety of tubes including a fuel filling pipe 11 are connected to a fuel tank 10 of an automobile. Specifically, one end of the fuel filling pipe 11 is connected to an aperture on a body of an unillustrated automobile, and a lid 12 is provided thereon. The other end of the fuel filling pipe 11 is inserted into the fuel tank 10, and a non-return valve 13 is fitted on a tip thereof.
Note that reference numeral 14 in FIG. 1 denotes a fuel supply pipe for supplying fuel to an injector of an unillustrated engine. A leader 14a thereof is attached to a chamber 15 disposed in the fuel tank 10. Moreover, reference numeral 16 denotes a fuel return pipe for returning the fuel unconsumed in the engine back to the fuel tank 10. In addition, reference numeral 17 denotes a vapor drawing pipe for guiding fuel vapor evaporated inside the fuel tank 10 out to an unillustrated canister.
From time to time, the fuel inside the fuel tank 10 is evaporated and thereby constitutes a high pressure. If the lid 12 of the fuel filling pipe 11 is opened in such a state, there is a risk that the fuel inside the fuel tank 10 flows back and erupts out of the aperture. The non-return valve 13 is provided to prevent flowing-back of the fuel as described above.
As an example of such non-return valves, there is Japanese Utility Model Laid-open Publication No. 7 (1995)-9637. In this example, the non-return valve includes a tubular case to be inserted into an end portion of a fuel filling pipe, and a valve element to be fitted into an aperture at one end of the case for closing the aperture. The non-return valve is disclosed therein, which is provided with a concave portion on an outer periphery of the case, and a flexible piece formed on an upper concave portion to be fitted into an engaging hole of the fuel filling pipe when the case is inserted into the fuel filling pipe.
However, the non-return valve as disclosed in the above-mentioned Japanese Utility Model Laid-open Publication No. 7 (1995)-9637 cannot prevent fuel and vapor thereof from flowing back from the outside of the fuel filling pipe inside the fuel tank to the inside of the fuel filling pipe through a gap between the fuel filling pipe and the tubular case, more particularly, through a gap between the engaging hole of the fuel filling pipe and the flexible piece of the case. For this reason, just as a tap of a fuel intake is released in a state of increased pressure inside the fuel tank owing to a high temperature, for example, then fuel droplets and vapor thereof suddenly erupt out into the atmosphere in the next breath.
In consideration of the foregoing problem, an object of the present invention is to provide a non-return valve for a fuel tank capable of sealing a downstream end portion of a fuel filling pipe more hermetically.
To attain the foregoing object, a first aspect of the present invention is to provide a non-return valve provided on a downstream end of a fuel filling pipe of a fuel tank, which includes a main tube to be inserted into the fuel filling pipe, a valve element provided on a downstream portion of the main tube, the valve element allowing fuel to flow into the fuel tank and inhibiting a back flow from the fuel tank, a first tube disposed between the main tube and the fuel filling pipe, the first tube including a first retaining portion relevant to the fuel filling pipe, an annular sealing member abutting on a peripheral face of the main tube and a peripheral face of the fuel filling pipe, and a second tube disposed at a position more upstream than the first tube so as to sandwich the annular sealing member together with the first tube, the first tube including a second retaining portion relevant to the main tube. Here, the first retaining portion of the first tube is engaged with and joined to the fuel filling pipe when the fuel filling pipe is inserted into the main tube.
According to the first aspect of the present invention as described above, when the fuel filling pipe is inserted into the second pipe from an upstream end portion of the main tube, a tip of the fuel filling pipe proceeds into the main tube through the second tube, the annular sealing member and the first tube and is engaged with and joined to the first retaining portion of the first tube. Therefore, the non-return valve for a fuel tank can be fitted onto the downstream end portion of the fuel filling pipe by a single action. Moreover, the annular sealing member seal closely contacts with the peripheral face of the fuel filling pipe and the peripheral face of the main tube and thereby sealing the both members, and a downstream side below the annular sealing member is completely covered with the main tube. In this way, it is possible to prevent a back flow of fuel and vapor thereof into the fuel filling pipe in the state where the non-return valve is closed, and to prevent sudden eruption of the fuel droplets and the vapor thereof out to the atmosphere when a tap of a fuel intake is released.
A second aspect of the present invention is to provide a non-return valve provided on a downstream end of a fuel filling pipe of a fuel tank, which includes a main tube to be externally inserted into and joined to the fuel filling pipe, a valve element provided on a downstream portion of the main tube for allowing fuel to flow into the fuel tank and inhibiting a back flow from the fuel tank, a first inner tube disposed between the main tube and the fuel filling pipe, the first tube including a first retaining portion relevant to the fuel filling pipe, an annular sealing member abutting on an inner periphery of the main tube and an outer periphery of the fuel filling pipe, and a second inner tube disposed at a position more upstream than the first tube so as to sandwich the annular sealing member together with the first tube, the second inner tube including a second retaining portion relevant to the main tube. Here, the first retaining portion of the first inner tube is engaged with and joined to the fuel filling pipe when the fuel filling pipe is inserted into the main tube.
According to the second aspect of the present invention as described above, since the non-return valve has a structure to insert the maim tube externally into the fuel filling pipe, a flow path for the fuel is not narrowed. Note that the first inner tube of the second aspect corresponds to the first tube of the first aspect, and the second inner tube of the second aspect corresponds to the second tube of the first aspect.
Moreover, a third aspect of the present invention is to provide the non-return valve for a fuel tank according to the second aspect, in which the first retaining portion includes an elastic retention arm protruding toward an inner diameter of the first inner tube and extending toward an upstream side so as to sandwich the fuel filling pipe, and a claw provided on an end portion of the first retaining portion is engaged non-rotatably with an engaging hole on the fuel filling pipe and thereby supports the fuel filling pipe by sandwiching between the elastic retention arm and an inner surface of the first inner tube.
According to the third aspect of the present invention as described above, the retaining portion of the first inner tube is formed of the elastic retention arm which protrudes toward the inner diameter and then extends toward the upstream side so as to sandwich the fuel filling pipe. Therefore, it is possible to secure a flexure margin for the elastic retention arm inside a tube path, and to provide the retaining portion relevant to the fuel filling pipe without affecting airtightness of the main tube.
In addition to the third aspect, a fourth aspect of the present invention is to provide the non-return valve for a fuel tank, which further includes rotation controlling means for controlling rotation of the main tube relative to the first inner tube, and depth controlling means for controlling a depth of insertion of the second inner tube with respect to the main tube.
According to the fourth aspect of the present invention as described above, the depth controlling means is provided in addition to the third aspect between the main tube and the second inner tube. Therefore, it is possible not to apply excessive pressure on the annular sealing member while securing an appropriate space between the first inner tube and the second inner tube. Moreover, the rotation controlling means between the main tube and the first inner tube can effectuate insertion of the first inner tube into the main tube at a proper angle with respect to the main tube.